Merge 3.9 RC5 fixes into master (#6459)

* UI fixes for 3.9 (#6400)

* UI fixes for header icon alignment

* PLT-6569 - Fixing pin icon in header

* PLT-6505 - Updating z-index for emoji picker

* Updating z-index for overlaying sidebar

* PLT-6134 - Fix for emoji picker on comments

* Reverting emoji picker fix

* Fixing alignment for header icons

* Removing channel title changes

* Don't show mention badge for active channel (#6411)

* PLT-6583 - Fixing RHS compact view (#6413)

webapp/sass/components/_emoticons.scss

@@ -143,15 +143,16 @@
 }
 
 .emoji-picker {
+    @include user-select(none);
+    border-radius: 3px;
+    border: 1px solid;
     display: flex;
     flex-direction: column;
-    @include user-select(none);
     position: absolute;
+    right: 0;
     top: -361px;
-    right: 0px;
     width: 278px;
-    border: 1px solid;
-    border-radius: 3px;
+    z-index: 8;
 
     .emoji-picker__search-container {
         position: relative;